1. Field
The present invention relates generally to the control of computer storage peripherals. More particularly, the invention relates to a computer software implemented method, product, and apparatus for scanning newly added disk drives and automatically rebuilding the configuration and configured data of a Redundant Array of Independent Disks (RAID) information.
2. State of the Art
Currently, many large data storage systems adopt a RAID approach. RAID is used for improving the I/O performance and data protection of mass storage devices. The advantage of using RAID technology, which groups disks with small storage capacity together to store a large amount of data and performs data access across multiple disks, lies in the fact that it can replace the use of an expensive large disk for data storage. At the same time, it can improve the efficiency of data throughput because the data access is performed only on each involved small disks. In other words, dividing data storage information into many small logical disk drive units in disk drives configured by RAID technology can not only reduce the cost but also speed up the access to the desired data distributed among various disk drives.
In a RAID configured environment, when some disk drives connected to the computer system have been ruined or disconnected, a user then connects new disk drives to restore the stability of the system. In order to maintain the consistency of data storage, the user rebuilds a new RAID configuration and integrates the configured data of those ruined and disconnected disk drives into the new configuration.
RAID technology is associated with RAID levels. Different levels provide different methods for creating redundant information for disk drives. When a disk drive is ruined or disconnected, redundant configured data is generated. This redundant data can be used to rebuild the configuration information completely according to the method provided. In general, there are four RAID levels but not limited to these four that are commonly used in the RAID technology, they are the RAID 0, RAID 1, RAID 5, and RAID 5 with hot spare, each provides various degrees of protecting data loss and capacity in data storage.
RAID 0 uses “stripping” where the data is distributed among a number of strips, which are stored across the disk drives in the array. This technique provides an approach for the simulation of a huge disk drive using as many as possible small disk drives to improve the performance of data accessing, but this technique provides no redundancy for the recovery of disk drives failure.
RAID 1 uses “mirroring” where each unit of data is duplicated to mirror onto another disk to protect data loss. The advantage of mirroring is that it provides very strong data protection. The drawback with mirroring is that it requires extensive disk storage redundancy achieving an efficiency of only half capacity of the storage system, even if there are n disks employed but only the mirrored one is used.
RAID 5 uses “parity” to configure a disk for the data redundancy. Each time an array is written in with configured data, RAID 5 generates redundant data to correspond to the written data and then stores the redundant data in a disk drive of equivalent size to that of one average disk drive. Consequently, if there are n disk drives in the array, there will be roughly n-1 disk drives space capacity for regular data storage. The advantage of this technique is that it offers fast throughput for small data files.
RAID 5 with spare uses one more disk drive to store redundancy in addition to the one that stores the generated redundancy by RAID 5 . If there are n disk drives in the array then there will be n-2 disk drive space capacity for regular data storage. This technique provides a stronger data protection than that of RAID 5 alone, and, at the same time, enjoys the same advantage of RAID 5.
There are two storage types: simple and span, which are not associated with RAID level, these non-RAID types of storage unit are also included in the present invention. Simple uses continuous space on a disk drive without redundancy data. Span concatenates storage units of simple type as a logical storage unit. The logical storage unit of type span has no redundancy data but provides flexibility for utilizing storage space.
A typical data storage system can contain a number of storage disks with drives. Storage of the configuration information associated with each disk drive may be arranged into logical disk drives or volumes with various RAID or non-RAID levels. A logical disk drive or a volume is formed by sub-drives of physical disk drives in a same disk drive group, and the volume layout structure of a disk drive group can be described by the constituent logical disk drives and structure of volumes in the group.
A RAID controller is a device that can be used to manage one or more arrays of RAID configured disk drives. However, if a system contains no RAID controller then a software program stored in the memory of a host computer can be implemented to behave as a RAID controller. Or, a computer software program can be implemented utilizing a CPU and memory of a computer system, including the CPU and memory of a RAID controller to manage the configuration of disk drives. The computer software program is for the purpose of configuring the physical disk drives in a computer system into logical disk drives where each logical drive is managed according to the associated RAID levels.
RAID configurations are complex and difficult to use when dealing with problems encountered in real applications. Part of the reason for these problems is that there are many possible ways to achieve a RAID configuration. Therefore, extensive knowledge and time is required of a user resolving the RAID configuration. Several RAID configuration methods have been proposed, such as Humlicek et al, U.S. Pat. No. 5,822,782 entitled, “Methods and Structure to maintain raid configuration information on disks of the array”; and Murthy et al, U.S. Pat. No. 6,092,169 entitled, “Apparatus and Method for storage subsystem drive movement and volume addition”. These two references solve a portion of the problem encountered in the application of the RAID configuration. However, their techniques are far from achieving the goal of an automatic RAID configuration.
Surugucchi et al, U.S. Pat. No. 6,098,119 entitled, “Apparatus and Method that automatically scans for and configures previously nonconfigured disk drives in accordance with a particular raid level based on the needed raid level” provides a technique that attempts to alleviate user input by automatically configuring both configured and un-configured disk drives at both system boot up and during runtime. However, this automatic configuration feature is very limited in dealing with the problems encountered during real applications. For example, in a real application when drive A leaves the system and drive B adds to the system to replace drive A; since both drives belong to the same disk drive group, both drives still retain their unique configuration identifiers. If later when drive A reenters the system, drive B has a new updated configuration information. Therefore, drive B instead of the drive A would be chosen for the configuration of the system. However, the method of Surugucchi et al, uses a set of combination rules according to small computer system interface (SCSI) channel and target identifiers as criterion for the selection of a disk drive among conflicted disk drives. These rules are dependent on RAID channels. They are not general enough to cover the users' expectation in real applications. Thus, in such a case, the Surugucchi et al method may not choose drive B for RAID configuration. Besides, in real applications, a storage system is usually connected to many different types of devices such as SCSI devices, Integrated Device Electronics (IDE) devices, and internet Small Computer System Interface (iSCSI) devices together, which make combination rules even more complicated and difficult to manage.
Accordingly, there exists a need for rebuilding a new RAID configuration when added disk drives are scanned and detected in real application to provide an automatic RAID configuration mechanism that can accommodate various types of RAID level configurations for a storage system having various physical dimensions. The device and method described below, provides such an invention.